A lawyer for Saif al-Islam Gaddafi, the son of the ousted Libyan dictator Muammar Gaddafi, has accused the authorities in his country of showing a "blatant disregard" for the international criminal court (ICC) by announcing they will put him on trial in August.

In an urgent submission to the Hague-based court, the British lawyer John Jones asked appeal judges to reject Libya's request to suspend an order that Tripoli surrender Gaddafi to the court.

Libyan officials are appealing against the international court's right to try Muammar's Gadaffi's erstwhile heir apparent, saying he should face justice at home, but the international court says Tripoli cannot give him a fair trial.

Jones says Gadaffi could be executed in Libya before the appeal is completed if he is not handed over to the court.

"The possible implementation of the death penalty in domestic proceedings would also create a grievous and irremediable consequence for Mr Gaddafi, and completely undermine the ability of the appeals chamber to render a determination on the appeal," Jones wrote.

Libyan prosecutors said on Monday that Gadaffi, along with the dictatorship-era spy chief, Abdullah al-Senoussi – who also is wanted by the ICC – the former premier al-Baghdadi al-Mahmoudi and the ex-spokesman Milad Daman, would be tried in August for crimes committed during Muammar Gaddafi's 42-year rule and the eight-month civil war that deposed him.

Jones said the announcement "could only be construed as blatant disregard" for Libya's obligations to the court.

Gaddafi is being held by a militia in the Libyan town of Zintan.

With no national army or police in place since the fall of Muammar Gaddafi's regime, successive governments have been too weak either to secure his son's imprisonment in the capital, Tripoli, or put pressure on his captors to hand him over to the government. Gaddafi is also being tried on separate charges of harming state security.